The present invention relates to a press driving module and to a method of providing a press line.
In the past, the slides of large-scale presses with a mechanical drive, as a rule, were connected by way of connecting rods with an eccentric drive which, in turn, was driven by a driving motor and a flywheel at a relatively uniform speed. Because such drives to an extent result in limitations with respect to the path-time course of the slide movement, efforts were made to drive the slide, for example, by way of a servo motor, in which case the path-time curve of the slide movement could then be relatively freely adjusted by the corresponding control of the servo motor. For this purpose, DE 41 09 796 C2, for example, discloses a drive of the slide by way of a connecting rod and an eccentric which is driven by a servo motor. The servo motor can run forward and backward and can be accelerated and decelerated in a targeted manner.
The same German patent document reveals the drive of the slide by way of a toggle mechanism which, in turn, is driven by a servo motor by way of a connecting rod and an eccentric. The desired path-time courses can be adjusted within wide limits also in this configuration.
U.S. Pat. No. 6,041,699 also discloses a slide drive of a press by way of servo motors and a toggle mechanism. A screw spindle mechanism and servo motors are used for driving the toggle mechanism.
Furthermore, JP 2000 343283 shows the drive of a press slide by way of spindle stroke mechanisms that are actuated by servo motors. This also achieves a largely free fixing of the path-time course of the slide movement.
The introduced solutions each suffer from specific limitations. If, for example, non-linear mechanisms, such as toggle mechanisms or eccentrics, are used for driving the slide, the slide movement is often not as freely adjustable as desired. In addition, the entire forming force has to be applied by the servo motor. The latter is disadvantageous particularly in the case of the last-mentioned drive concepts. Although non-linear drives, such as toggle mechanisms or eccentric mechanisms, permit a higher force to be generated in the proximity of the dead center, this takes place only along a relatively short path. The drive of the press slide by way of the spindle stroke mechanism, on one hand, permits a very free fixing of the path-time course of the slide movement but limits the maximal force which can be applied before the lower dead center is reached.
An object of the present invention is to improve the randomly controllable press drive.
This object has been achieved by a press driving module, a first characteristic force-path curve, a second driving device operatively connected at least with another of the at least one first and second outputs and has a second characteristic force-path curve different from the first characteristic force-path curve, wherein the press driving module is a constructional unit. In addition, the present invention is achieved with a method of producing a press line having several presses in which the aforementioned first and second characteristic force-path curves are used and uniform driving modules are used in different numbers.
The press driving module according to the present invention is a combination of two driving devices which have different force-path curves. This is preferably achieved by utilizing different driving concepts. As a result, not only path-time courses of the slide movement which are arbitrary within wide limits can be reached, but that driving device which has the currently fitting characteristic for each part of the path-time curve can be used. For example, for rapidly passing through characteristic curve sections requiring only a low actuating force, a weak but fast drive can be used. For carrying out forming operations which, as a rule, is to be carried out without interruption but nevertheless relatively slowly but at a high force, that driving device can be used which applies a high force while the working speed is relatively low.
In the simplest case, the two driving devices, which are combined in the press driving module, can be formed, for example, by servo motors with a gearing on the output side and different gear ratios. The servo motors may have the same or a different construction. As a result of the different gear reduction, the servo motors, although they act upon the same output, operate in different characteristic curve ranges while the output speed is the same, which, on the whole, increases the design space with respect to the achievable path-time courses of the slide movement. In addition, the margin with respect to the achievable forces is increased.
The above-indicated press driving module is therefore versatile and can be used as a basis for equipping differently sized presses of a press line. On one hand, with the given press driving module, a large range of desired forces and traveling speeds can be achieved. On the other hand, unless prevented by constructive or other limits of practicality, any number of press driving modules can in principle be connected in parallel. Thus, a press slide can be driven by one or more identical press driving modules, whereby different performance classes can be provided within a press line. Furthermore, it becomes possible to provide driving modules in different performance classes, the driving modules being uniform within each performance class.
As a result of the combination of several driving modules from one or two or more performance classes and the large performance range of each press driving module, all presses of the press line can therefore be equipped with the standardized press driving modules. A press working line can therefore be constructed whose first station (drawing station) has a larger number of press driving modules, while the subsequent, as a rule, less loaded press stations are equipped with correspondingly fewer press driving modules. In the individual stations of the press line, different slide path-time courses and different slide strokes can be driven in this case.
It is particularly expedient for the performance classes of the provided press modules having a uniform maximal stroke to be exponentially graduated. As a result of the combination of press driving modules of different performance classes, many different applications can therefore be permitted. The performance classes of the driving modules are determined, for example, by the maximal forces to be applied by the driving modules. In this case, even the driving modules of different performance classes preferably have the same maximal stroke. This permits the combination of press driving modules of different performance classes with one another for forming the common drive of a slide of a press. Furthermore, the press driving modules of the different performance classes preferably have the same maximal displacement rates. Like the uniformly defined maximal stroke, this facilitates the parallel arrangement for the common drive of one and the same slide.
The press driving modules each form constructional units, which are preferably constructed separately from the press. They can therefore be prefabricated and be installed as a finished module in correspondingly prepared press frames. The press driving modules can be assembled separately from the press frame. This is important particularly in the case of large-scale presses. This concept can lead to a simplification of the production and shorten the construction time of presses.
For many purposes, it is advantageous for at least one of the driving devices of the press driving modules to contain a gearing with a variable ratio. This can, for example, be a toggle mechanism, an eccentric mechanism, and combination thereof or another gearing with a variable ratio. These are particularly gearings which supply an infinitely large power ratio or, in other words, a fixed supporting point in their dead center or reversal point, in that the force to be supported is no longer determined by the driving servo motor but only by the loading limits of the gearing. This is important, for example, in the case of solutions in which the driving devices are constructively arranged in series. For example, a servo-motor-driven eccentric drive can be connected in series with a hydraulic cylinder. While the eccentric drive then has the purpose of rapidly driving the slide in ranges of its movement curve at a relatively low force, the hydraulic driving device can have the purpose of slowly driving the slide for the workpiece forming at a high force. If, in this case, the eccentric is in the dead center position, the servo motor remains essentially free of forces. It therefore becomes possible, with relatively weak servo motors and a relatively short-stroke hydraulic device, to generate a large movement stroke for the slide, on one hand, and a high forming force, on the other hand. This advantage can also be achieved used other serially arranged driving devices.
Particularly in the case of serially arranged driving devices, it may be advantageous to activate these successively with respect to time. The two different driving devices are therefore responsible for different sections of the path-time curve of the slide movement. In the transition range from the activation of one driving device to the activation of the other driving device, both driving devices can be activated in an overlapping manner.
Particularly in the case of a parallel arrangement of the two driving devices, these are preferably activated jointly, supplementing one another with respect to developing their force.
It is advantageous for the press driving module to have a separate base frame which takes over the guidance between the two outputs. Furthermore, a housing can be provided in which the at least two driving devices are accommodated. As an alternative, however, it is also contemplated to integrate the press driving module at least partially in the press frame. For example, one of the outputs can be constructed as part of a press head piece or slide.
Preferably an energy accumulator, such as a mechanical, electric or hydraulic energy accumulator, is assigned to the press driving modules. This minimizes the supply system loading.
In principle, the press module may have many different constructions. Almost all embodiments, however, have the characteristic that the introduction of force of the at least two driving devices pertaining to the module takes place at the slide and/or at the head piece in each case at a common point. In addition, the press driving modules define a fixed numerical ratio between the number of the first driving devices and the number of the second driving devices. If a slide is driven, for example, only by driving modules of a single performance class which each, for example, have s first driving device and a second driving device, irrespective of the number of press driving modules, on the whole, just as many first driving devices as second driving devices are present for driving the slide.
If press driving modules are conceived with, for example, a first driving device and two or more for example, three second driving devices and are used for driving the slide, in the example, three times as many second driving devices are present as first driving devices. If press driving modules of different performance class and with different ratios between the numbers of the first and of the second driving devices are used, these numerical ratios in each case apply in groups to the press driving modules of the respectively considered performance class.
The driving devices of the press driving module are preferably mechanically independent of one another; that is, they can be controlled independently of one another. The synchronization of their working movement or their coordination preferably takes place electrically. The individual modules or also just their driving devices or drives can be actuated depending on the design or, as required, also switchably optionally in a path-controlled and/or force-controlled manner. They preferably permit a continuous adjustment of the slide stroke during the operation as well as a variation of the characteristic path-time curve of the slide movement during the operation. Force sensors can be provided for avoiding overloads particularly in the case of driving modules or driving devices driven in a path-controlled manner.
In addition, the individual driving devices of a press driving module can be rigidly connected with one another. As an alternative, they may be coupled with one another by coupling devices of an arbitrarily controllable type or by overrunning clutches. For example, in the case of a parallel arrangement of two driving devices, the slow driving device can be uncoupled from the fast-running driving device if a rapid traveling along a slide path is required. The slow drive is then coupled again when the fast drive has moved the slide back onto the uncoupling point and a large force is required during the slow slide movement.
In a serial arrangement of two driving devices in a press driving module, the fast driving device can be braked by a braking device when a slow working movement at a high force is to be generated. The stronger of the two driving devices is then not only supported on the first driving device but, in addition, or even exclusively, by the braking device. Thus, the above-mentioned coupling devices and braking devices can have the purpose of making the slide movement more efficient.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.